I recently ran across this blog (www.maskcara.com). It is full of awesome resources on hair and makeup. I highly recommend checking it out if you are wondering how to look your best in your next portraits, she even has a post on how to do your make up for photos.
The blog is written by Cara, she is a makeup artist and not only teaches you how to do your makeup but also what makeup to buy and how to make some of your own.
Another article I would highly recommend checking out is Highlighting and Contouring, this is how you do your makeup to give your face definition. Cara explains it as the difference between us and the celebrities.
More great stuff from Cara:
Put on False Lashes
Makeup for Hazel Eyes
Makeup for Blue Eyes